Feed chute booster for flexible strap



Sept. 23, 1969 J. H. LESLIE ET AL FEED CHUTE BOOSTER FOR FLEXIBLE STRAP3 Sheets-Sheet 1 Filed Feb- 19. 1968 050;! lyzdia/z/d W My Q TTOP/VEKSSept. 23, J H, LESUE ET AL FEED CHUTE BOOSTER FOR FLEXIBLE STRAP 3Sheets-Sheet 2 Filed Feb. 19. 1968 Sept. 23, 1969 .1. H. LESLIE ET3,468,241

FEED CHUTE BOOSTER FOR FLEXIBLE STRAP Filed Feb. 19, 1968 3 Sheets-Sheet3 United States US. Cl. 100-26 13 Claims ABSTRACT OF THE DISCLOSUREBooster mechanisms are disclosed to assist the pushfeeding of flexiblestrap through strap chutes. Thin flexible strap of plastic or steel isfed through longer chutes by locating one or more boosters at spacedlocations along the chute to subdivide the strap chute travel path intosuccessive regions, each region being a substantial fraction of thetotal path. These different booster mecha nisms are shown. In one form,a fixed motor drives a traction wheel that is nested within the chuteand a cooperating idler wheel is mounted for movement between a feedposition confronting the chute and a retracted position that allowsclearance for stripping of the strap from the chute. In another form, amotor and a multilobed traction wheel are mounted for joint movementbetween a feed position wherein the traction wheel is in confrontingrelation to the chute and a clearance position. The multilobed wheelloads the strap directly against the chute and produces an intermittentfeeding action tending to vibrate and shake the strap so as to reducefriction. In a third embodiment, a pair of power-driven traction Wheelscooperate to drive the strap, these wheels being of rubber, to permit acertain amount of skidding against the strap when tending to overdrivethe strap. The booster traction wheels operate at slightly greater speedthan the feed rate of the strapping machine.

BACKGROUND OF THE INVENTION This invention relates to strappingapparatus such as is employed at a strapping station for forming a loopof flexible strap about an object located at the station. Typically, thestrapping station includes a chute defining a strap travel pathencircling the object and the strapping apparatus includes strap infeedmeans adjacent the chute for pushing the strap through the chute to forma complete loop.

At present, it is quite difiicult to push-feed the thinner sizes ofplastic or steel strap through long strap chutes, or even throughshorter chutes having sharp corners. The longer the chute and the moresharp turns therein, the greater the frictional resistance presented bythe chute to movement of the strap as it is being pushed therethrough.Ultimately, the frictional resistance to the strap movement accumulatesto a level tending to cause the strap to buckle locally within thechute, with each occurrence of buckling adding to the total resistanceto the strap movement and aggravating the strap feed problem.

The strap feeding problem encountered in high resistance chuteconfigurations is most pronounced in the case of the thinner sizes ofnylon or polypropylene strap, for example, 0.015 to 0.020 inch,particularly where widths as small as A1 inch are employed. Plasticstrap in these sizes is notably subject to camber or curl leading to anexaggerated lateral wedging action of the strap edge against the chutewall so that an increased chute resistance effect results.

Where the strapping station is equipped with power driven strap feedingequipment conventionally operating at a uniform feed rate, thearrangement is more subject to buckling of the strap for a given chuteconfiguration atent O than is the case where manual strap feed isemployed. In a manual feed operation, intermittent jiggling and shakingof the strap during push-feeding thereof tends to disrupt progressiveaccumulation of frictional resistance such as naturally arises inconnection with the uniform feeding action of power equipment.

SUMMARY OF THE INVENTION The present invention provides a boostermechanism for assisting lengthwise feed of the strap through the chute.The booster is associated with the chute for establishing push-feedingengagement with strap intermediately along the chute effectively tosubdivide the total strap chute travel path into successive regionsthrough which the strap is pushed first by the infeed means and then bythe booster. Where longer chutes and higher resistance chuteconfigurations are involved, the invention contemplates the use ofadditional boosters as needed, each subtending a chute region thatrepresents a substantial fraction of the total strap chute travel path.In general, the boosters are located at the end of a straight chutesection to assure feeding of the strap around the adjacent corner.

The booster mechanisms as disclosed herein operate at a strap feed rateslightly greater than that of the main infeed device.

Two booster embodiments disclosed herein are driven by a slip type drivesystem to adapt automatically to the strap supply condition at theparticular region of the chute. In one of these embodiments, amotor-driven traction wheel is stationed within the chute to engage thestrap from one surface and load it against an idler wheel that ismounted for movement between a feed position facing the strap chute anda retracted position to permit the strap to be stripped from the chuteand drawn taut about the object. In the second embodiment, a singlemotor-driven traction wheel of a lobed configuration is mounted formovement between a feed position facing the chute and a retractedposition.

A third embodiment utilizes a pair of rubber traction wheels, bothpower-driven, to permit a certain amount of skidding against the strapwhen there is a tendency to overdrive the strap.

The strap chute may be of a conventional type that includesspring-loaded side gates that control the strap during lengthwise traveland during stripping from the chute, the gates being modified at thebooster region to provide access for the traction wheel.

Other features and advantages of the invention will be apparent from thefollowing description and claims and are illustrated in the accompanyingdrawings which show structure embodying preferred features of thepresent invention and the principles thereof, and what is now consideredto be the best mode in which to apply these principles.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings froming a partof the specifictaion, and in which like numerals are employed todesignate like parts throughout the same,

FIG. 1 is a diagrammatic front elevational view of a strapping stationhaving a rectangular chute encircling an object supported at thestation, the station being equipped with a power strapping head thatpush-feeds strap into and through the chute and a pair of boosters thatare spaced along the chute to assist in push-feeding strap therethrough;

FIG. 2 is an enlarged fragmentary view taken approximately as indicatedon the line 2-2 of FIG. 1 and disclosing a two-wheel embodiment of abooster in accordance with this invention;

FIG. 3 is a transverse section through the booster and is taken asindicated on the lines 33 of FIG. 2;

FIG. 4 is a diagrammatic view corresponding to that of FIG. 1 andshowing a chute equipped with a pair of boosters;

FIG. 5 is an enlarged fragmentary view taken as indicated on the line 55of FIG. 4 and disclosing an alternative booster embodiment employing asingle-lobed type traction wheel;

FIG. 6 is an end elevational view of the booster embodiment shown inFIG. 5;

FIG. 7 is a fragmentary front elevational view taken as indicated on theline 7-7 of FIG. 5;

FIG. 8 is a fragmentary transverse section taken as indicated on theline 88 of FIG. 7; and

FIG. 9 is a fragmentary sectional view corresponding to the views ofFIGS. 2 and 5 and showing a third embodiment utilizing a pair ofpower-driven rubber wheels.

Referring now to the drawings, typical power strapping stations aredesignated generally at 10 in FIGS. 1 and 4. Each strapping station 10is illustrated diagrammatically as including a conventional strap feedchute 11 of rectangular configuration encircling an object 12 supportedat the station in position to receive a loop of strap S.

A power strapping mechanism 13 of any conventional type is shownassociated with an access region along the lower run of the chute 11and, as is well known, the strapping mechanism 13 includes infeed meansfor pushing strap lengthwise through the chute in the directionindicated by the arrows A to form a complete loop about the object.Typically, a power strapping head such as any one of units of theSignode model M-ZO series may be utilized for this purpose, the headalso including a tensioning mechanism for taking up the slack loop tostrip the strap from the chute and shrink the loop about the object anda sealing mechanism for securing the overlapping ends of the strap loop.

The chute structures 11 may be of any conventional type and, as shownherein, are comprised of a back up element 14 flanked by successivepairs of angle-shaped side gates 15 mounted to the back up element by aplurality of spring-loaded bolt assemblies 16. Each mounting boltassembly 16 typically includes a through bolt 16B and a pair of springs16S acting between each end of the bolt and the corresponding side gate15, as best shown in FIG. 5.

In conventional operation of the strapping equipment, the strap ispush-fed lengthwise through the chute with the strap leading endreturning to the power head 13 to complete a slack loop. The power headthen draws tension on the slack loop to strip the strap from the chuteand shrink it into tensioned relation about the object and thereafterthe overlapping portion of the loop is sealed and the supply end cut tocomplete the operation.

As mentioned previously, in the case of chutes of longer sizes, or withsharp corner bends, particularly in strapping applications involving thehandling of thin plastic strap subject to camber and curl, theaccumulation of resistance to push-feeding of the strap can lead tobuckling of the strap within the chute. In accordance with the presentinvention, buckling is avoided by subdividing the chute into successiveregions, each of which has means for pushing the strap lengthwisetherethrough. The chute arrangement shown in FIG. 1 is equipped with asingle booster 20 for this purpose, this booster being of the typerepresented in FIGS. 2 and 3 and the chute arrangement shown in FIG. 4is equipped with a pair of boosters 30, each being of the type shown inFIGS. 5 through 8. The boosters are located at the end of a straightchute section to insure feed of the strap around the succeeding comer. Asingle booster is used for a short chute, two for an intermediate sizechute and three for large chute systems.

The booster arrangement 20 shown in FIGS. 2 and 3 has a main mountingplate 21 secured to the chute and serves to support a fixed motor M thatdrives a traction wheel 22 nested within a generally circular cavitydefined by an interrupted region in the back up element 14. An

idler wheel 23 is mounted on a swing arm 24 to be movable between a feedposition, as shown in full lines in FIG. 2, facing the strap chute in aretracted position, as shown in phantom lines in FIG. 2. In thisretracted position, there is sufiicien-t clearance to strip the strapfrom the chute onto the object 12. The swing arm 24 is pivoted on themounting plate by a pivot pin 24F. The mounting plate 21 includes an endextension 21E serving as a rigid seat for a load spring 25 that normallyreacts against the swing arm to bias it towards its feed positionindicated by a full line where it holds the strap against the tractionwheel 22.

In this embodiment, the strap in exiting from the strap chute contactsthe idler wheel 23 and forceably swings it towards its retractedposition. Any suitable control may be provided to energize the motor foroperation only during the time that the strapping head 13 is in itsstrap feed cycle. As is best shown in FIG. 3, the guide flanges 15F onside gates 15 are interrupted to provide an access window for the idlerwheel 23 which is to enter the chute sufficiently to press the strap Sagainst the traction Wheel. The side gate 15 on the motor side of thechute is interrupted as necessary to provide sufiicient clearance forthe side gate to swing open during stripping of the strap. The frame 14is shown with tipped frontal portions 14T beveled slightly relative tothe line of travel of the strap S through the booster station andarranged in close clearance to the traction wheel periphery to insuresmooth snag-free passage of the lead end of the strap.

The provision of one or more boosters of this type at suitably spacedregions along the chute serves to subdivide the chute into shortersections and prevents any accumulation of chute resistance great enoughto cause buckling of the strap. As illustrated in FIG. 1, the strappinghead 13 serves to feed the strap through an initial region amounting toalmost one-half of the total chute travel path and the booster 20handles the remainder. In other configurations, the strapping head 13may account for a greater fraction of the total chute travel path thandoes the booster but, in either case, each feed mechanism works inseries with the remainder and serves to feed strap over a substantialfraction of the total travel path.

The motor M is equipped with a slip clutch in its drive connection tothe traction wheel 22 and is operated at a speed to provide a boosterfeed rate slightly greater than the feed rate of the strapping head.Slack buildup between the feed stations is thereby avoided, precludingone possible source of buckling and actually tending to increase theeffective feed range of the strapping head.

The booster 30 shown in FIGS. 5 to 8 utilizes a single traction wheel 31located to face the chute to load the strap S directly against the backup element 14. The traction wheel is of a multilobed type and in theembodiment disclosed herein has four symmetrically spaced arcuatetraction surfaces 31T separated by relieved regions 31R. Only thetraction surfaces 31T produce feeding of the strap so that themultilobed wheel provides an intermittent feeding action which serves tosimultaneously shake and vibrate the strap, thereby overcoming anytendency to bind. Any number of lobes operating in accordance with thesame principle can be provided on the traction wheel. In this form, theside gates 15 of the chute are interrupted only at their front flangeportions 15F to provide an access window for the traction wheel to loadthe strap against the back up element 14. A mounting plate 32 is shownsecured to the back up element 14 and extends laterally of the chute toprovide a pair of ofiset mounting ears 32E that carry a pivot pin 32?for a mounting car 3313 on a swing bracket 33. The motor M has its basebolted directly to the swing bracket 33 so that in this embodiment, themotor M and the tracion wheel 31 are movable between the feed positionillustrated in full lines in FIG. 5 and the retracted positionillustrated in phantom lines in FIG. 5. The position of the motor iscontrolled by a double-acting hydraulic cylinder 34 shown supportedbetween flanking lug portions 32L on the rear of the mounting plate. Thecylinder 34 has a piston rod 35 leading through the mounting plate andpivotally connected to a drive car 33D on the swing bracket.

In this embodiment, the motor M runs continuously to drive the tractionwheel 31 and the cylinder operation is timed by any suitable means (notshown) to hold the traction wheel in feed position during the time thatthe strapping head 13 is in its strap feed cycle and to move thetraction wheel to its retracted position to accommodate stripping of thestrap from the chute when the strapping head draws tension on the loop.The position control on the cylinder sets the traction wheel at aposition wherein a permanent minimum clearance is maintained between thetraction wheel periphery and the back up element 14. This clearance isslightly less than the strap thickness so that the traction wheel loadsthe strap against the back up element to effect lengthwise feeding ofthe strap through the chute. The motor M again includes a slip clutchdrive and is operated at a speed to produce a feed rate that averagesout to the feed rate of the strapping head. Thus, during the intervalswhen the arcuate traction regions 31T are engaging the strap, the strapis advanced more rapidly than it is being fed and a bulged region ofstrap tends to develop on the downstream side of the traction wheel.Then during the passage of the relieved lobe region 31R wherein nofeeding occurs at the boster, the strap is paid out from the bulgedslack to the next booster. The side gate flanges 15]? are shown withoblique wing portions 15W to allow the slight bulging action withoutcausing snagging or buckling.

Another booster embodiment 40 is shown in FIG. 9, wherein a pair ofcooperating traction wheels 41, 42 are both power-driven to act againstopposite faces of the strap S. A main mounting plate 43 secured to thechute 11 serves to support a fixedly mounted motor M. The traction wheel41 is nested within a suitable cavity defined by an interrupted regionin the chute and is powered by the drive shaft 44 of the motor M.

The mounting plate 43 is shown provided with a support arm 43A thatcarries a sleeve type pivot bearing 45 in which a companion drive shaft46 is journaled. Mating friction drive wheels 44F and 46F are shownengaged intermediately along the shafts 44, 46 to drive the shaft 46from the shaft 44. The traction wheel 42 is mounted on the drive shaft46 to be swingable about the axis of the pivot bearing 45 for movementbetween a feed position, as shown in full lines in FIG. 9, and aretracted position (not shown) affording sufficient clearance to stripstrap from the chute and onto the object being secured.

A compression spring mechanism 47 is carried by the mounting plate 43and normally acts through a ring bearing 48 on the end of the shaft 46to resiliently bias the same to the parallel position as illustratedwherein the friction wheels 44F, 46F are urged together more tightlythan the loading of the traction wheels 41, 42. For this purpose, thetraction wheels 41, 42 are of slightly less diameter than the frictionwheels 44F, 46F and are of a rubber or rubber-like material to becapable of skidding movement relative to the strap. Correspondingly, thefriction wheels are of an antiskid material.

The motor M is driven at a speed to rotate the traction wheels 41, 42 ata feed rate slightly greater than the feed rate of the strapping head.Slack buildup is thereby avoided, as stated previously, and in thisembodiment the pair of powered traction wheels aifect a more balancedfeed action to the strap and yet allow a certain amount of skidding asdetermined by existing conditions of each application.

In the embodiment of FIG. 9, the motor M runs continuously to drive thetraction wheel 41 at all times, while the spring mechanism 47 normallybiases the shaft 46 to its illustrated position for driving the tractionwheel 42 in synchronism. During stripping of the strap from the chute,the movement of the strap forcibly swings the traction wheel 42 out ofits power-driven relationship and toward a retracted relation thatallows the strap to pass around the wheel 42 and seat on the package.

What is claimed is:

1. In strapping apparatus for forming a loop of flexible strap about anobject located at a strapping station that includes a chute defining astrap travel path encircling the object, said apparatus including mainfeed means, adjacent an entry region of said chute for pushing straplengthwise through said chute to form a slack loop, means for drawingtension on said slack loop to strip the strap from said chute and shrinkthe same about said object, and booster mechanism for assistinglengthwise feed of said strap and including at least one traction wheelmounted for push-feeding engagement with strap intermediately along saidchute.

2. In strapping apparatus in accordance with claim 1 wherein said chutehas a rectangular configuration that includes elongated straightsections and corner sections and said booster mechanism is located alonga straight section adjacent the downstream end thereof.

3. In strapping apparatus in accordance with claim 1 and wherein saidbooster mechanism operates said traction wheel at a strap feed rateslightly greater than the feed rate of said main feed means.

4. In strapping apparatus in accordance with claim 1 wherein saidbooster mechanism has slip-type drive means normally operating saidtraction wheel at a strap feed rate slightly greater than the feed rateof said main feed means.

5. In strapping apparatus in accordance which claim 1 wherein saidbooster mechanism has said traction wheel mounted in interposed relationin said chute to engage a face of the strap in said chute, and includesmeans mounting an idler wheel for movement between a feed positionfacing said traction wheel and a retracted position spaced therefrom toaccommodate stripping of the strap from said chute through said feedposition.

6. In strapping apparatus in accordance with claim 5 wherein thelast-named means comprises a swing arm pivotable about an axis parallelto and olfset from the plane of said chute and rotatably carrying saididler wheel and spring means yieldably biasing said spring arm in adirection to load said idler wheel towards said traction wheel forengaging the strap therebetween.

7. In strapping apparatus in accordance with claim 5 wherein saidbooster mechanism has slip-type drive means normally operating saidtraction wheel at a feed rate slightly greater than the feed rate ofsaid main feed means.

8. In strapping apparatus in accordance with claim 1 and wherein saidbooster mechanism includes means mounting said traction wheel formovement between a feed position facing the strap and a clearanceposition spaced therefrom to accommodate stripping of the strap fromsaid chute through said feed position.

9. In strapping apparatus in accordance with claim 1 wherein saidtraction Wheel is of multi-lobed configuration having alternate tractionregions and relieved regions to provide an intermittent feeding actiontending to vibrate and shake the strap to reduce friction.

10. In strapping apparatus in accordance with claim 9 and wherein saidbooster mechanism includes means mounting said traction wheel formovement between a feed position facing said chute wherein said tractionwheel has a position maintaining substantial contact against the strapand a clearance position spaced therefrom to accommodate stripping ofthe strap from said chute through said feed position.

11. In strapping apparatus in accordance with claim 1 wherein saidbooster mechanism comprises a cooperating pair of power-driven tractionwheels, one mounted in interposed relation in said chute and meansmounting the other traction wheel for movement between a feed positionfacing the chute and a retracted position spaced therefrom toaccommodate stripping of the strap from said chute through said feedposition.

12. In strapping apparatus in accordance with claim 11 wherein thelast-named means includes a shaft pivotable about an axis parallel toand offset from the plane of the chute carrying the other traction wheelin frictionally driven relation to the first traction wheel and springmeans yieldably biasing said shaft in a direction to load said tractionwheels against the strap.

13. In strapping apparatus in accordance with claim 1 References CitedUNITED STATES PATENTS O BILLY J. WILHITE, Primary Examiner 2,707,429 5/1955 Leslie 100-226 XR 5 2,968,982 1/1961 Cousino 226-413 XR 3,037,6906/ 1962 Tailleur 226-1 13 XR 3,196,779 7/ 1965 Embree 100-26 XR

